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Comparison of Ocean Surface Solar Irradiance in the GLA General Circulation Model and Satellite-based Calculations

Beth ChertockWave Propagation Laboratory, NOAA/Environmental Research Laboratories, Boulder, Colorado

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Y. C. SudLaboratory for Atmospheres, NASA/Goddard Space Flight Center, Greenbelt, Maryland

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Abstract

A global, 7-year satellite-based record of ocean surface solar irradiance (SSI) is used to assess the realism of ocean SSI simulated by the nine-layer Goddard Laboratory for Atmospheres (GLA) General Circulation Model (GCM). January and July climatologies of net SSI produced by the model are compared with corresponding satellite climatologies for the world oceans between 54°N and 54°S. This comparison of climatologies indicates areas of strengths and weaknesses in the GCM treatment of cloud-radiation interactions, the major source of model uncertainty. Realism of ocean SSI is also important for applications such as incorporating the GLA GCM into a coupled ocean-atmosphere GCM. The results show that the GLA GCM simulates too much SSI in the extratropies and too little in the tropics, especially in the summer hemisphere. These discrepancies reach magnitudes of 60 W m−2 and more. The discrepancies are particularly large in the July case off the western coast of North America. In this region of persistent marine stratus, the GCM climatological values exceed the satellite climatological values by as much as 131 W m−2. Positive and negative discrepancies in SSI are shown to be consistent with discrepancies in planetary albedo.

Abstract

A global, 7-year satellite-based record of ocean surface solar irradiance (SSI) is used to assess the realism of ocean SSI simulated by the nine-layer Goddard Laboratory for Atmospheres (GLA) General Circulation Model (GCM). January and July climatologies of net SSI produced by the model are compared with corresponding satellite climatologies for the world oceans between 54°N and 54°S. This comparison of climatologies indicates areas of strengths and weaknesses in the GCM treatment of cloud-radiation interactions, the major source of model uncertainty. Realism of ocean SSI is also important for applications such as incorporating the GLA GCM into a coupled ocean-atmosphere GCM. The results show that the GLA GCM simulates too much SSI in the extratropies and too little in the tropics, especially in the summer hemisphere. These discrepancies reach magnitudes of 60 W m−2 and more. The discrepancies are particularly large in the July case off the western coast of North America. In this region of persistent marine stratus, the GCM climatological values exceed the satellite climatological values by as much as 131 W m−2. Positive and negative discrepancies in SSI are shown to be consistent with discrepancies in planetary albedo.

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